iv had 3 engineers out to my boiler because every four days the pressure had droped to zero. they checked the safety valve and replaced the expansion vessel, and it still droped every four days. they all agreed i had a leak however after taking all the floors up no leak was found. my plumber then capped off all the radiators except one which was not leaking and in four days it had droped to zero, we are at a loss what to do next.

mrs bolland, June 2009

is it a condensing boiler?? if so the heat exchanger could possibly be leaking and going out of the condensate?? isolate your boiler from the central heating circs ( close off flow and return valves) leave for 4days and then see if it still drops. if it does drop then the leak is clearly on your boiler, if not then its on the system

xpert, June 2009

I'm wondering here (depending on the age of your boiler) if the heat exchanger is losing water internally, and the loss is being expelled out of your chimney as steam? Everything else seems to have been covered!

John, June 2009